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Bio 2D03 > Lecture 6 > Flashcards

Lecture 6 Flashcards

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Biology 101 flashcards
1
Q

what external signals do plants respond to?

A

temperature, wind, CO2, pathogens, water status, mineral nutrients, light levels, light quality, day length, gravity, humidity, herbivores, O2 levels in soil

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2
Q

ability to perceive light and hormones affects what developmental responses?

A

seed germination, seedling development, shade avoidance, phototropism, stomatal opening, chloroplast movements, flowering,

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3
Q

Role of light:

A

energy: photosynthesis
information: photomorphogenesis

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4
Q

photoreceptors

A

detect different wavelengths of light; photoreceptors, signal transduction pathway, response

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5
Q

skotomorphogenesis

A

light seeking response, etiolated, grow towardslight

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6
Q

etiolation:

A

hypocotyl becomes long and spindly, seedling is pale yellow (no chloroplast), apical hook forms in dicots,

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7
Q

exposure of skotomorrphogenesis plant to light

A

etiolated sidelight switches to photomorphogenesis and becomes de-etiolated

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8
Q

de-etiolation

A

chloroplast development, hypocotyl stops growing, SAM initiates leaf production

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9
Q

SAM

A

shoot apical meristem

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10
Q

phytochrome receptors:

A

apoprotein and chromophore

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11
Q

Pr phytochrome

A

chromophore absorbs red light

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12
Q

Pfr phytochrome

A

chromophore absorbs far-red light

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13
Q

phytochrome interconversion

A

in the presence of red or far red light, Pr and Pfr forms interconvert in which the chromophore undergoes a cis-trans isomerization leading to conformational change in the protein part of the phytochrome

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14
Q

R:FR

A

ratio of red to far red light which is perceived by phytochrome to elicit a response

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15
Q

phytochrome receptor functions

A

germination–small seeds with small endosperm require light to germinate

seedling establishment–etiolated to de-etiolated or non photosynthetic to photosynthetic or skotomorphogenesis to photomorphogenesis

architecture of plant–shade avoidance

initiation of flowering and seed dormancy

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16
Q

PIFs

A

polychrome interacting factors; small gene family of transcription factors

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17
Q

competitive shade avoidance response

A

grow out of shade into sunlight to promote photosynthesis, growth, and reproduction. triggered by low R:FR values because chlorophyll absorbs red light and reflects far-red light

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18
Q

features of shade avoidance response

A

growth of stem, growth of petioles, inhibition of leaf expansion, early flowering

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19
Q

Trigger of shade avoidance:

A

in shade a plant will have more Pr than Pfr because of the low R:FR indicating that reduction in active Pfr initiates shade avoidance

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20
Q

what phytochrome are involved in shade avoidance?

A

PHYB, PHYD, PHYE all act redundantly and have a major role in shade avoidance

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21
Q

PHYB

A

is a major contributor to shade response in shade and it inhibits shade response in daylight

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22
Q

PHYD and PHYE

A

contribute less to shade response in shade and they are not involved in inhibiting shade response in daylight

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23
Q

PHYB mutant arabidopsis plant

A

shade response reduced but still observed in shade

shade responce observed in daylight

24
Q

response pathway in daylight

A

R>FR – PHYB Pr absorbs light – interconverts to PHYB P fr – negative regulation occurs – PIFs do not facilitate shade response

25
Q

response pathway in shade

A

R

26
Q

Phototropism

A

directional growth towards a light source
more cell growth on one side of the stem to bend it
increases opportunity for light capture + photosynthesis
triggered by blue light

27
Q

PHOT1 and PHOT2 function

A

gene products of PHOT1 and PHOT2 are required for phototropic response, chloroplast movement and stomatal opening responses. Evidence from PHOT1&2 double mutant which failed to present any of these responses

28
Q

Phototropic 1&2 receptors description

A

blue light photoreceptors with redundant functions

plasma membrane associated

kinase domain phosphorylates itself after blue light absorbed

auxin gradient produced by higher auxin on shaded sides promoting cell elongation bending stem towards light

29
Q

phytohormone ethylene gas functions

A 
seedling germination
abscission of leaves and fruits
senescence of leaves and fruits
response to pathogen attack
regulation of fruit ripening
30
Q

ethylene phytohormone in seedling development

A

seedling is wounded while pushing through soil, ethylene is produced, ethylene signal transduction pathway is initiated, seedling triple response occurs

31
Q

seedling triple response

A

allows seedling to force its way through soil and provides protection for Shoot Apical Meristem SAM

32
Q

features of seedling triple response

A

hypocotyl becomes shorter and thicker
roots become shorter and thicker
apical hook becomes exaggerated

33
Q

genetic mutant screens

A

screen through many seedling with different but unknown mutations looking for seedlings with a specific mutant such as mutant triple response phenotype

34
Q

etr1 mutant

A

no triple response when exposed to ethylene; ethylene-insensitive mutant; encodes a receptor kinase protein that binds to ethylene

35
Q

ctr1 mutant

A

triple response in absence of ethylene; constitutive triple response mutant

36
Q

ethylene stp

A

(signal transduction pathway) no ethylene–ethylene receptors active–activate CTR1, a negative regulator of ethylene response

37
Q

CTR1

A

negative regulator of ethylene STP

38
Q

describe what happens when ethylene is present

A

ethylene binds to ethylene receptors, ethylene receptors phosphorylate making them inactive. Inactive receptors are unable to activate CTR1 so CTR1 is in turn unable to inhibit the downstream ethylene STP function resulting in an ethylene response occurring

39
Q

is ethylene response positively or negatively regulated?

A

the ethylene receptors negatively regulate CTR1 which negatively regulates the STP. each step is negatively regulated, however the presence of ethylene overall positively regulates the ethylene response.

40
Q

RAN1

A

probably supplies ETR1 with copper ions required in ethylene binding site

41
Q

EIN2

A

membrane spanning protein downstream of CTR1, function unknown

42
Q

senescence

A

aging resulting in deterioration of biological function

43
Q

what would be observed in a EIN2 loss-of-function mutant in the presence of ethylene for the seedling triple response?

A

because ein2 is located downstream of CTR1, loss of its function would result in the signal not being transduced causing the seedling to be unable to display the triple response. CHECK THIS ANSWER

44
Q

temperate climate seeds

A

undergo maturation drying to promote dormancy and seed longevity. become dormant at end of seed development to prevent fall germination allowing overwinter. embryo survives in seed for long time without water due to seed desiccation and drought tolerance

45
Q

tropical plant seeds

A

germinate as soon as seeds mature

46
Q

ABA

A

abscisic acid; promotes dormancy and inhibits germination

47
Q

GA

A

gibberellin or gibberellin acid; promotes: germination, mobilization of seed reserves, cell expansion in growing seedlings, glowering

48
Q

VP1

A

regulates expression of ABA inducible genes during seed maturation in corn and arabidopsis

49
Q

GA biosynthesis mutant

A

seeds that don’t germinate

50
Q

GA insensitive mutants

A

seeds that germinate poorly

51
Q

ABA biosynthesis mutants

A

seeds that germinate sooner than wt

52
Q

ABA insensitive mutants

A

seeds that germinate when wt does not

53
Q

ga mutants

A

low GA–no germination unless GA is added

54
Q

aba ga mutants

A

low GA and low ABA levels–germination occurs without adding GA

55
Q

ratio of GA to ABA

A

it is a balance of GA and ABA that regulates germination, not absolute levels; GA and ABA act antagonistically

56
Q

Outline the process from seed development to seedling development in reference to GA and ABA

A
  • ABA promotes desiccation tolerance and dormancy
  • ABA is reduced and GA is increased causing dormancy to end
  • GA promotes reserve mobilization
  • GA promotes growth and cell expansion during development of seedling
57
Q

what is actively repressing the triple response genes

A

Etr1 and CTR1 both actively repress the triple response genes

Bio 2D03 (10 decks)

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